This invention relates to a video and audio data processing method and apparatus by which digital data representative of a video signal and digital data representative of an audio signal are processed so as to have a format for transmission thereof through a data transmission line such as a coaxial cable.
In order to allow transmission of digital video data (DV data) and digital audio data (DA data) obtained by digitizing a video signal and an audio signal which make signal elements which form a television broadcasting signal and representative of the video signal and the audio signal, respectively, through a data transmission line formed from, for example, a coaxial cable, the DV data and the DA data are normally processed so that they may have a format set in advance. Various formats are available for the format, and a format called serial data interface (SDI) format has been proposed as one of such formats.
In order to transmit DV data and DA data using the SDI format, the DV data and the DA data to be transmitted are divided into and placed as a series of successive data segments DP each of which corresponds to a one line period (1 H) beginning with a horizontal synchronizing signal SSH of a video signal SV. Each data segment DP includes an EAV part of a 4 word-structure, an ancillary area part of a 268 word-structure, an SAV part of a 4 word-structure and a payload area part of a 1,440 word-structure and is totally composed of 1,716 words.
In each data segment DP, DV data are placed for 1,440 words in the maximum in the payload area part, and DA data are placed for 268 words in the maximum in the ancillary area part. Where the DV data and the DA data to be transmitted are a video signal and an audio signal which form a television signal conforming to the NTSC system, DV data for a one frame period of the video signal (for the first and second field periods) and corresponding DA data are placed in 525 successive data segments DP.
FIG. 2 illustrates an example of a condition wherein DV data for a one frame period of a video signal and corresponding DA data are placed in 525 successive data segments DP. It is to be noted that reference symbol NL in FIG. 2 represents the number of each data segment DP. In the example illustrated in FIG. 2, DV data for a 240 line period which is a first field period for the video signal are placed in the payload area parts of 244 data segments DP beginning with the 20th one and ending with the 263rd one of the 525 successive data segments DP, and DA data corresponding to the DV data are placed in the ancillary area parts of the 244 data segments DP beginning with the 20th data segment DP and ending with the 263rd data segment DP. Further, DV data for another 240 line period which is a second field period for the video signal are placed in the payload area parts of 243 data segments DP beginning with the 283rd one and ending with the 525th one of the 525 successive data segments DP, and DA data corresponding to the DV data are placed in the ancillary area parts of the 243 data segments beginning with the 283rd data segment DP and ending with the 525th data segment DP.
When transmission of DV data and DA data is performed using the SDI format in such a manner as described above, data segments DP in the payload area parts of which the divided DV data are placed and in the ancillary area parts of which the divided DA data are placed are successively transmitted through data transmission lines. In this instance, one set of DV data and DA data is transmitted for each one data transmission line. Accordingly, in order to transmit a plurality of sets of DV data and DA data which are different from each other substantially simultaneously or in a common transmission period, a plural number of data transmission lines equal to the number of sets of DV data and DA data are required even if the data are to be transmitted to a common transmission destination.
For example, in order to transmit 10 sets of DV data and DA data substantially simultaneously or in a common transmission period to a common transmission destination, 10 data transmission lines are required, and if it is assumed that each of the data transmission lines is formed by a coaxial cable, then it is required to lay 10 coaxial cables. To provide a plurality of data transmission lines each formed from, for example, a coaxial cable in this manner gives rise to complication and increase in scale of an apparatus or equipment for data transmission and further to an increase in cost for data transmission.